1. Field of the Invention
The present invention relates to a mobile communication system, a local subscriber information management device, and a communication information management method.
2. Description of the Related Art
There is a mobile communication system constructed to include a subscriber original record information management device which manages subscriber original record information that contains original record information of information representing respective mobile terminals and subscriber information corresponding to these mobile terminals, and a local subscriber information management device which acquires subscriber management information that contains information representing the respective mobile terminal that is a visiting mobile terminal and subscriber information corresponding to the respective mobile terminal from the subscriber original record information management device and manages the acquired subscriber management information.
In a mobile communication system conforming to 3GPP (3rd Generation Partnership Projects) recommendation, an HLR (Home Location Register) scheme and a VLR (Visitor Location Register) scheme are defined as schemes for managing a position of a mobile terminal and subscriber information.
In the HLR scheme, information that is an original record of position information of a mobile terminal and subscriber information is managed in an HLR installed physically independently from a mobile switching center.
In the VLR scheme, on the occasion of location registration of a relevant mobile terminal, subscriber information is downloaded from an HLR (i.e., copied from the above described original record) into a VLR of a respective mobile switching center which the mobile terminal has visited, and manages the position information and subscriber information of the mobile terminal.
Incidentally, there is an increasing number of cases where a wireless terminal device having a function as a mobile terminal is provided in a vending machine such as of beverages or cigarettes and is used for inventory control and user authentication.
In the cases as described above, it is allowed to supply a vending machine with sales items according to a current stock instead of based mainly on experience of an operator in a conventional manner, and the security is ensured to a certain extent.
The application of a mobile terminal (wireless terminal device) as described above tends to spread over general-purpose equipment such as household electrical appliances.
The number of mobile terminals accommodated in mobile communication systems is rapidly increasing partly because such a mobile terminal includes not only a device carried by a user but also a device incorporated in various equipment such as a vending machine and general-purpose equipment as described above. This significant increase is easily predicted to be far beyond the increase of actual data traffic.
Specifically, for example, as a mobile terminal carried by a user moves literally, a corresponding current mobile switching center is frequently changed in succession, and only due to this, traffic of management information frequently occurs. In contrast, with respect to a vending machine or general-purpose equipment, the probability of changing a current mobile switching center is very low in a normal operation or use situation, and therefore traffic of management information regarding this changing rarely occurs.
However, in a design philosophy about conventional mobile communication system operation, the above described local subscriber information management device (VLR in a mobile communication system conforming to 3 GPP recommendation) is assumed to reserve a memory capacity corresponding to the number of mobile terminals.
Toward the forthcoming ubiquitous age, if facilities are added to the local subscriber information management device (VLR) according to the substantial increase of the number of mobile terminals to be accommodated in the mobile communication system, there is a problem that terribly unreasonable excessive facilities are built with respect to actual communication traffic of data.
There has been proposed a technique in which a situation where any more registration into a current mobile switching center (or its VLR) is not allowed is assumed to occur, and when this situation occurs, subscriber information which can be erased without trouble is erased so that free space is reserved.
For example, at a mobile switching center, if subscriber information cannot be newly registered in a first management device for the mobile switching center which manages subscriber information when a location registration signal is received from a mobile terminal, one item of subscriber information currently registered in the first management device for the mobile switching center is deleted to reserve a free space for registration, and subscriber information is registered after the free space is reserved (see JP 2002-320032 A, especially paragraphs 0054 to 0065, FIGS. 9 to 12, and others).
In addition, it has been proposed that at a mobile switching center, if subscriber information cannot be newly registered in a management device for the mobile switching center which manages subscriber information when a location registration signal is received from a mobile terminal, such subscriber information is registered in a management device for another mobile switching center which manages subscriber information.
In this proposal, if subscriber information of a mobile terminal that has sent a transmission signal is not registered in a management device for a mobile switching center which manages subscriber information when the transmission signal is received from the mobile terminal, the subscriber information of the mobile terminal is acquired from a management device for another mobile switching center which manages subscriber information (see JP 2006-5966 A, especially paragraphs 0007 to 0008, 0049 to 0054, 0128, 0248 to 0251, and 0319, FIGS. 6 to 8, and others).
In addition, there has been proposed a technique in which, in a mobile communication system where a plurality of switches manage areas and each mobile switching center retains subscriber information of a mobile terminal visiting in an area managed by the mobile switching center, a communication controller forwards a location registration signal from a mobile terminal to a destination mobile switching center depending on free space of area subscriber information retaining means, and notifies the mobile terminal of the destination mobile switching center which has performed location registration.
In this proposal, it is said that, even if free space of area subscriber information retaining means of one mobile switching center is small, a location registration signal can be forwarded to another mobile switching center so that location registration of a mobile terminal can be performed. And furthermore, since a communication controller notifies a mobile terminal of the destination mobile switching center which has performed location registration, the mobile terminal can send a signal to the destination mobile switching center which retains the subscriber information of the mobile terminal in the area subscriber information retaining means after the location registration, mobile communication service can be provided to more mobile terminals, and connection delay and increase of the amount of signal at sending and receiving can be prevented (see JP 2006-074404 A, especially paragraphs 0020 to 0028, FIGS. 1 and 2, and others).
However, in any of the techniques disclosed in the above patent documents, a situation where any more subscriber information cannot be registered in a current mobile switching center or a subscriber information management device (local station's VLR) is assumed to occur, and when this situation occurs, subscriber information which can be erased without trouble is erased so that free space is reserved and then subscriber information is registered in this mobile switching center or subscriber information management device, or subscriber information is registered in another mobile switching center or subscriber information management device (local station's VLR). Thus, the above-described techniques are not intended to provide a method to prevent or reduce the occurrence of the “situation where any more subscriber information cannot be registered”.